The aims of this study are: 1) to identify patients at highest risk of sudden death from ventricular arrhythmia following an acute myocardial infarction, and 2) to reduce the incidence of this complication in those patients identified to be at highest risk. The study population will consist of approximately 425 survivors of myocardial infarction who have one or more conventional risk factors for subsequent sudden cardiac death. These patients will receive electrophysiologic study (EPS) with programmed ventricular stimulation; Up to 3 ventricular extrastimuli will be administered in an attempt to induce ventricular tachycardia (VT). Those patients without inducible VT will be teated with a beta adrenergic blocking agent only. Of the patients with inducible VT at EPS, one group will receive beta blockade therapy only, while another group will receive EPS-guided antiarrhythmic therapy in additional to beta blockade. These three groups will be followed long-term to determine whether the results of EPS predict subsequent sudden cardiac death more accurately than current techniques, and whether prophylactic therapy guided by EPS can prevent sudden cardiac death in susceptible patients.